6.4. Hashtable Values

Hashtables are tables that map keys to values. You can define a hashtable with the Hashtable() function. To enter and retrieve values you use the put and get functions, and with the keys function you can retrieve a list of all keys in the table:

.define ht {
    // Define the table
    .var ht = Hashtable()

    // Enter some values (put(key,value))
    .eval ht.put("ram", 64)
    .eval ht.put("bits", 8)
    .eval ht.put(1, "Hello")
    .eval ht.put(2, "World")
    .eval ht.put("directions", List().add("Up","Down","Left","Right"))

    // Brief ways of initialising tables
    .var ht2 = Hashtable().put(1, "Yes").put(2, "No")
    .var ht4 = Hashtable().put(1,"a", 2,"b", 3,"c")

// Retrieve the values
.print ht.get(1)    // Prints Hello
.print ht.get(2)    // Prints World
.print "ram = " + ht.get("ram") + "kb"    // Prints ram=64kb

// Print all the keys
.var keys = ht.keys()
.for (var i=0; i<keys.size(); i++) {
    .print keys.get(i)    // Prints "ram", "bits", 1, 2, directions

When a value is used as a key then it is the values string representation that is used. This means that ht.get(“1.0”) and ht.get(1) returns the same element. If you try to get an element that isn't present in the table, null is returned.

Table 6.3. Hashtable Values

Function Description
put(key,value) Maps 'key' to 'value'. If the key is previously mapped to a value, the previous mapping is lost. The table itself is returned.
put(key,value,key,value,key,value....) Maps several keys to several values. The table itself is returned.
get(key) Returns the value mapped to 'key'. A null value is returned if no value has been mapped to the key.
keys() Returns a list value of all the keys in the table.
containsKey(key) Returns true if the key is defined in the table, otherwise false.
remove(key) Removes the key and its value from the table.